Conventional taps as described in Australian Standards 1718-1988 and 3718-1988 comprise a metal body having an inlet end which is connectable to a supply pipe, an outlet end in the form of a spout, and a passageway extending between the inlet and outlet ends. An opening (hereinafter referred to as a valve port) is provided in the passageway, which is surrounded on its upper surface by an annular valve seat. A valve member is carried by a spindle which is engaged in threaded relationship with a spindle housing, and the spindle can be turned in one direction to drive the valve member against the valve seat and thereby "close" the tap. The tap is "opened" by turning the spindle in the opposite direction.
The valve member usually comprises a resilient washer which is carried on a loose jumper valve which is connected to its valve stem, and the stem is slidable in the spindle. Thus, when the tap is opened, the spindle is screwed in a direction away from the valve seat and the valve member is forced open against the spindle by water pressure.
The tap as above described would normally form one of a network of taps throughout a building. Thus, the water pressure which would be acting on the valve member in any one tap will be dependent upon the number of taps which are opened and closed in the network.
In some situations, taps are left permanently open, for example when they are attached via hoses or other pipes to domestic washing machines and/or dishwashers etc. In-line taps are also used to isolate certain areas of a building and/or to isolate toilet cisterns and hot water services. In these situations, where no water is flowing through the taps, a valve member may be fully open or closed, or be in a floating intermediate position. Then, should a sudden increase in water pressure occur, for example when a tap in another location is quickly turned off resulting in a shockwave being created within the pipe, the increased pressure will force the valve member to slam against the spindle or valve seat. The noise produced by this phenomenon is commonly referred to as water hammer and can be a source of considerable annoyance in a household or other situation because of the level of noise produced. Water hammer is just one of numerous problems which are prevalent in taps which utilize conventional valves. Some of the more common problems associated with conventional valves are listed as follows:
1. Many taps are difficult to turn on and off and this problem is compounded with wear and tear of the washer. PA0 2. Many valves and washers have a low service life. PA0 3. Washers are usually less efficient as they become older and more worn. PA0 4. Valves vary in efficiency from hot to cold water. PA0 5. Conventional valves usually cause water noise when a tap is turned on. PA0 6. Because of the rotational friction that exists when turning on and off a tap, the valve seat of a tap is usually worn away as well as the valve washer. PA0 7. In taps which are part of a pipe network backfeeding or backsyphonage can also occur. PA0 8. Conventional tap valves cannot effectively handle wide fluctuations in water pressure as small movements of the tap handle and spindle result in coarse adjustments of water flow. PA0 9. Older taps often continue to drip even when turned off firmly. PA0 10. Taps, like those found on the boundary of a property (meter taps), which are left open for years suffer from washer deterioration. When these taps are eventually turned off they leak badly.